Digital-to-analog converters (DACs, D/A-converters) constitute a basic building block in modern integrated-circuit (IC) design, since they form the ubiquitous digital-to-analog interface in digital transceivers and digitally aided control loops. Current steering DACs are used whenever a certain minimum sampling speed is required.
In general, a current-steering DAC responds to a digital input code by outputting a current that is proportional to the digital representation. Thus, the magnitude of the output current changes with changes to the digital input code. Moreover, in certain current-steering DACs that implement multiple current cells, any of the current cells may switch output states in response to a digital input code, producing a variable current output from a varying digital input.
In contrast to, for example, switched-capacitor realizations, standard implementations of current-steering DACs are be transparent for non-ideal error signals that are generated during code changes, i.e. when the DAC switches from one input code to the next. These errors may include switch injection, asymmetries in the ON/OFF transitions, settling of internal nodes, and other non-ideal effects generated during switching of the current cells. Because the number of current cells that switch during a transition is dependent on the input code sequence, nonlinear distortion may result from these effects.